1. Field of the Invention
The present invention relates to the field of telecommunications. More particularly, the present invention relates to a method for multi-user telecommunications.
2. Description of the Related Art
Currently, there are three major non-random multiple access techniques for multi-user communications: FDMA, TDMA and CDMA. In multimedia transmissions, i.e., applications having different data rates, none of these three multiple access techniques is effective in terms of throughput efficiency, hardware implementation, or signal quality. For instance, to accommodate a high bit rate data type, an FDMA approach assigns several frequency subbands that are separated by frequency guardbands and are realized by distinct carriers, resulting in spectral and hardware inefficiency. Similarly, a TDMA approach uses several time slots that are separated by time guardbands and requires accurate timing at both the transmitter and receiver. TDMA leads to throughput loss and intersymbol interference caused by channel distortion, multipath spread, and mistiming. Lastly, a CDMA approach breakdowns the high-rate bit stream to several lower-rate bit streams for achieving a sufficiently large processing gain. Each low-rate stream requires spreading and despreading processing. The breakdown to several low-rate streams is also necessary if dynamic assignment of any data types to a CDMA channel is to be achieved. Further, the performance of a CDMA rake receiver degrades considerably in the presence of intersymbol interference.
What is needed is an effective and efficient multiple access technique for multi-user communications that is resistant to intersymbol interference occurring in high-speed transmission, and accommodates multiple user data rates, while keeping hardware implementation simple.